Method and apparatus of furnace operation



y 1965 w. L. LIVINGSTON ETAL 3,192,985

METHOD AND APPARATUS OF FURNACE OPERATION Filed Feb. 14, 1962 NGE WILLIAM L. LIVINGSTON MATHEW P STENGEL LARRY 0. MO NAIR INVENTORSZ BY [16,! 6. M ATTORNEY United States Patent O 3,192,985 BETHGD AND APPARATUS F FURNACE OPERATION William L. Livingston, Bloomfield, Mathew P. Stengel,

Windsor, and Larry D. McNair, West Hartford, Conn,

assignors to Combustion Engineering, Inc., Windsor,

Conn., a corporation of Delaware Filed Feb. 14, 1962, Ser. No. 173,202 15 Claims. (Cl. 158-1) This invention relates generally to the art of furnace operation with the furnaces being of the type wherein fuel and air are introduced thereinto with the fuel being burned therewithin. The invention has particular relation to an improved process and system wherein the furnace atmosphere is inerted under certain operating conditions, such as at a flame-out and at start-up with the atmosphere being tested or analyzed to insure that it is rendered nonfiammable by the inerting system and to further provide an indication that the inerting system has been effective to purge the furnace of any flammable fuelair mixture. The invention further has relation to the method and apparatus for testing the furnace atmosphere to determine the aforementioned characteristics.

As disclosed and explained in copending application Serial No. 173,204 filed February 14, 1962, entitled Method and Apparatus for Operating Furnace filed concurrently herewith, in order to insure safety of operation of a furnace, such as a furnace of a steam generator under all operating conditions, the inerting of the furnace is an extremely desirable procedure. For example in the start-up of a furnace in order to purge the furnace atmosphere, an inert gas may be introduced thereinto to eflect this result after which the light off procedure may be followed. Also in the event of a flame-out in a furnace,

the inerting of the furnace may be provided by introducing an inert gas thereinto.

incident to inerting a furnace it is desirable to determine, during the inerting process, whether or not the atmosphere has actually been renderednonflammable by the introduction of the inert gas. It is also desired to know whether or not the inerting operation has been carried on for a sufiicient length of time so that the furnace has been purged of any flammable fuel air mixture that might have been contained therein. With the present invention these characteristics of the furnace atmosphere are determined during the purging operation. In accordance with the invention a sample of the furnace atmosphere is withdrawn from the furnace and passed through a combustion zone or chamber which is provided with asuitable igniter. If the atmosphere is flammable a flame will be produced in this first zone indicating that the inerting process or system has not been effective to inert the furnace and a greater quantity of inert gas is necessary. After traversing this first combustion zone or chamber this furnace atmosphere sample is passed through a zone or device which is elfective to remove the inerting gas which has been added to the furnace atmosphere by the inerting system. In the event that steam is used as the inerting gas the removal thereof inrthe sample maye be effected by means of condensing the steam from the sample. After thus removing the inert medium from the sample the sample is then passed through a second combustion zone or chamber. This zone or chamher is also provided with a suitable igniter and if the sample burns in this second zone it indicates that the inerting medium has been effective to inert the furnace atmosphere since if combustion takes place in the second zone it will be absent in the first zone since otherwise the burnables therein would be burned in the first zone and there would be nothing to sustain combustion in the second zone. How- '2-2 of FIG. 1; and

FIG. 3 is a sectional .view taken generally along-line ever, combustion in the second zone indicates that in the absence of inerting medium added to the furnace at flammable mixture is present in the furnace atmosphere or in other words the furnace has not been purged of a flammable mixture and introduction of the inert medium to the furnace should be continued until there is no combustion in the second zone. The presence or absence of combustion in the first and second zones in the testing system is continuously determined and this may be through visual means or through a suitable detector indicating whether or not flame combustion is present.

Accordingly, it is an object of this invention to provide an improved process and system for the operation of a furnace including an inerting arrangement together with 'means for testing the furnace atmosphere during the inerting process.

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

scription of an illustrative embodiment, said embodiment being shown by the accompanying drawing wherein:

FIG. 1 is a generally diagrammatic representation of a furnace of the steam generator equipped with the organization of the present invention;

FIG. 2 is a sectional view taken generally along line 33 of FIG. 2.

Referring now to the drawing, wherein like reference characters are used throughout to designate like elements,

the illustrative and preferred embodiment as depicted therein includes a furnace designated generally 10 and into which fuel is introduced by burner 12 with the fuel 1 being supplied through the fuel pipe 14 and nozzle 16 and with air being supplied by means of forced draft fan 18 which forces the air through the duct 20 into the distribution duct or wiudbox 22 from whence it passes through opening 24 in the furnace wall on into the furnace. The flow of. fuel through pipe 14 is controlled by valve 26 and the supply of air to the burner may be adjusted by means of the adjustable damper 28.)

The furnace it; forms a portion of the steam generator, the steam generating circuit of which includes the tubes 30 disposed along the inner surface of the wall of the generator and which connect into a suitable header 32 from which the working fluid of the steam generator is conveyed to chamber 34. V

In order to inert the atmosphere in the furnace, in the illustrative.organization, steam is introduced into the Windbox 22although it is to be understood that other inerting gaseous medium may be employed. However, steam is ideally suited for this purpose and has a particular advan- 'tage in combination with a stem generator because of its availability at suitably elevated pressures. V

In the illustrative arrangement there is provided in the windbox 22 the distribution conduit 36 which has suitable openings throughout its length and which is connected to receive steam from chamber 34 by means of introduced. The air is effectively blocked in the Windbox 22 by introducing suflicient steam therein so that the steam provides a backpressure against which the fan 13 must operate with this backpressure being sufficient to block a substantial portion of the air formerly admitted to the furnace as aforesaid.

The invention may be employed to inert the furnace during initial light off or incident to a flame-out. With regard to this latter, a flame detector 42 may be utilized to detect the presence or absence of flame in the furnace with there being several different types of such detectors commercially available so that the details thereof are not shown and described herein. This detector may provide a signal when the flame is lost which may be effective through controller 44 to open the valve .0 and close the fuel control valve 25. When inertingthe furnace during initial light off the supply of inert gas must be a separate source other than that normally prevailing in the chamber 34 during operation of the steam generator. This separate source may be another adjacent steam generator or may be a specially provided source of inert gas.

in order to determine Wiener or not the inerting system has been effective to inert the furnace atmosphere so that it is nonflammable and also to sufiiciently purge the furnace atmosphere of a nonflammable mixture there is provided the testing or inert provin system identified generally as 46. This system includes a first combustion Zone or chamber 48 which is connected with and communicates with the interior of the furnace chamber through the connecting duct or conduit 50. At the upstream and of the combustion chamber 48 there is provided a suitable igniter which may take a variety of forms,

such as a hot wire, or a spark igniter operative to continuously provide a spark during operation of the testing system. This spark igniter is shown in FIGURES 2 and 3 and includes the spark plug 52 mounted in a suitable bracket or stand 54 which in turn is attached to an asbestos ring 56 that is secured within the cylindrical chamber 48. The plug 52 is secured to the stand or bracket 54 by means of the plate members 58 which are secured to the spark plug and clamp the bracket therebetween. The spark plug is connected with a suitable electrical conduit 59 which extends to and is connected with a source of alternating or interrupted electrical potential. The sample from furnace is sucked through the chamber 48 by means of the fan 66 and after traversing the combustion chamber 48 it passes through the inert gas removing portion of the testing system with this portion being identified as 62. In the illustrative organization wherein steam is employed as the inerting gas this portion 62 of the testing apparatus takes the form of a condenser which, as disclosed, is a conduit in the form of a coil 64 into which cooling fluid or the condensing medium is supplied through the inlet 66 and is withdrawn through the outletportion 68 of the conduit. After passing through this portion 62 of the system wherein the inerting steam is removed from the sample, the gas sample is then conveyed through the second combustion zone or chamber 70 which is provided with a suitable igniter such as spark plug 52 at its upstream end in the same manner as the first-mentioned combustion chamber 48. After traversing this second combustion chamber the gas sample is exhausted through the fan 60. V

In the operation of the organization of the invention the furnace atmosphere is tested to determine whether or not the inerting medium introduced into the furnace is effective to actually inert the atmosphere of the furnace and further to determine whether or not the furnace has been completely purged of a flammable fuel-air mixture.

During activation of the inerting system the testing system 46is maintained in opcraton. If burning takes place in the first combustion chamber 43 the operator then knows that inerting of the furnace has not been accomlished and accordingly a greater quantity of inert gas must be supplied. If burning does not take place in the first combustion chamber but does take place in the second combustion chamber where the sample of th furnace atmosphere is that which would prevail if there were no inerting medium added the operator then knows that the incrting is effective to render the furnace atmosphere noncombustible and that without the inerting medium a combustible fuel-air mixture is present in the furnace wherefore the introduction of the iiert gas must be continued in order to adequately purge the furnace of a flammable fuel air mixture.

In utilizing this system with a 60,080 lb. per hour steam generator it is found that a fan or? having a capacity of cubic feet per minute is more than adequate and gives satisfactory results with the flow velocity through th testin system then being about 15 feet per second so that a furnace gas sample is tested in less than one second with rapid testing being extremely desirable.

'In the illustrative organization, the combustion charrbers 455 and T3 are formed of visor glass tubes so that a visual indication of the presence or absence of combustion in each of the zones is provided. Other ways of providing an indication of the presence or absence of flame in the combustion chambers may be equally well employed, as for example, the arrangement disclosed in copending application Serial No. 77,375 filed December 21, i960, now Patent No. 3,115,403, may be utilized along with combustion chambers formed by means of steel tubular members in lieu of said glass members. Accordingly, it will be evident that with the organization of the present invention there is provided an improved method and combination wherein the atmosphere of a furnace is inerted and during the inerting is tested to determine the characteristics thereof with regard to the adequacy of the inerting and the flammability of the atmosphere in theabsence of iuerting.

While we have illustrated and described a preferred embodiment of our invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention.

' We therefore do not wish to be limited to the precise details set forth but desire to avail ourselves of such changes as fall within the purview of our invention.

What we claim is: V

1. In combination a furnace into which fuel and air are introduced with the fuel being burned therewithin, means for introducing into the furnace an inert gas and means for sampling the furnace atmosphere including burner means for burning the furnace atmosphere as received from the furnace, means operative to remove the inert gas added to said atmosphere and means receiving the atmosphere with the inert gas thus removed and effective to ignite and burn the same if it is flammable.

2. The organization of claim 1 wherein the furnace forms a portion of a steam generator and wherein inerting is effected by providing means for conveying steam generated in the generator and introducing it into the furnace.

3. The organization of claim 2 wherein the furnace is provided with a burner that includes duct means for conveying to and introducing combustion supporting air into the furnace with means being provided to introduce the inerting steam into this duct means.

i. The organization of claim 1 wherein the means for introducing inert gas into the furnace includes means to introduce steam thereinto as the inert gas and wherein the furnace atmosphere sampling means includes first burning means, a condenser and second burning means in series flow relation with regard to the traverse of the furnace sample with ignition means being provided in each of the burner means.

5. A steam generator comprising in combination a furnace burner means including means for introducing combustion supporting air and means for introducing fuel into the furnace for burning therewithin, means for inerting the system to prevent an explosion therein including means to convey steam generated in the steamgen erator into the furnace, means for controlling the introduction of this inert medium into the furnace, means for withdrawing gases from the furnace to test the flammability thereof including a first ignition and burning means, a second ignition and burning means and a condenser interposed therebetween and means associated with each of the burner means operative to indicate the presonce or absence of combustion in the respective burner means.

6. In the operation of a furnace the method comprising introducing fuel and combustion supporting air into the furnace and burning the fuel therewithin, incident to a flame-out introducing an inert gas into the furnace to render the atmosphere therein nonfiammable, testing the flammability of the furnace atmosphere by conveying at least a portion thereof through a first zone and attempting to ignite the same, removing the inert gas from this .portion of the furnace atmosphere after traversal of said first zone and conveying the remaining gases to a second zone and for attempting to ignite the same.

7. The process of claim 6 wherein the inerting gas is steam and wherein the removal of the inerting gas from the furnace atmosphere portion that has traversed said first zone is effected by condensing the steam in this atmosphere portion and removing the condensate therefrom.

8. In the operation of a furnace within which fuel and air are introduced and the fuel normally burned the process of inerting the furnace comprising introducing thereinto an inerting gas, testing the furnace atmosphere to determine whether the inerting has successfully rendered the atmosphere inert and to determine whether the inerting has continued suificiently long to purge the atmosphere of a flammable fuel-air mixture comprising withdrawing a portion of the atmosphere and conveying it through a first zone and then through a second zone, attempting to ignite the atmosphere in each of said zones, removing the inerting gas from the atmosphere portion thus withdrawn intermediate said zones.

9. The method of claim 8 wherein the inerting gas is steam and the removal of the steam in said portion of the sample withdrawn is effected by condensing the steam and removing the condensate from said sample.

10. The process comprising providing a stream of air, introducing this air along with fuel into a confined volume and burning the fuel therein with the air supporting combustion thereof, continuously determining whether or not the fuel is burned and in the event the burning ceases discontinuing the introduction of said fuel, introducing inert gas stream into the air stream to substantially block said stream and introducing the inert gas into said confined volume to render the contents thereof nonflammable, testing the gases in said volume to determine the nonfiammability thereof by withdrawing a sample of the gases through a first zone and attempting to ignite the same, thereafter removing the inerting gas from the sample and passing the sample through a second zone and attempting to ignite the same in this second zone, with the presence or absence of flame in these two zones being determined.

11. The process of continuously testing the atmosphere of a furnace that has been inerted by a suitable inerting phere is rendered nonfiammable and whether or not in the absence of the inerting medium the furnace atmosphere is nonflammable comprising a first combustion zone, passing a sample of the atmosphere through a firstzone and attempting to ignite the same therein, thereafter passing this atmosphere through an inert removing zone wherein the gaseous medium employed for inerting the furnace atmosphere is removed from the sample and thereafter passing the sample through a second zone and attempting to ignite the same therein with the presence or absence of flame in each of the zones being continu ously determined during the testing.

12. Apparatus for testing a furnace atmosphere comprising means forming a first combustion zone including igniter means, means forming a second combustion zone also including igniter means, and a condenser connected intermediate and separating said two zones and through which the gas when passing from the first to the second zone must pass with the means forming the combustion zones being constructedand arranged to provide an indication of the presence or absence of combustion in each of said zones.

13. In combination a furnace into which fuel and air are introduced with the fuel being burned therewithin, means for testing the'furnace atmosphere including means for sampling the gases in the furnace and comprising burner'means for burning the furnace gases as received from the furnace, means operative to removejan inert gas from the gases discharging from the last mentioned burner means, and means receiving the remaining gases I cluding igniter means, means forming a second combustion zone also including igniter means, means disposed intermediate said .zone means and separating the same operative to remove an inert gas from the furnace atmosphere when said atmosphere is directed therethrough from the first to the second zone with the combustion zone means being constructed and arranged to provide an indication of the presence or absence of combustion in each of said zones.

15. In the operation of a furnace the method of testing the furnace atmosphere comprising conveying a portion externally thereof and through a first zone and attempting to ignite the same, conveying said portion through a second zone and removing an inert gas therefrom and thereafter conveying the remaining portion with the inert gas thus removed through still another zone andattempting to ignite the same.

References Cited by the Examiner UNITED STATES PATENTS 1,746,123 2/30 Lopez 122504.3 2,341,727 2/44 Krogh. 2,532,214 11/50 Willenborg 158123 2,533,339 12/50 Willenborg 158-123 2,585,882 2/52 Weissman et al 158--l23 FOREIGN PATENTS 843,342 8/60 Great Britain.

JAMES W. WESTHAVER, Primary Examiner.

PERCY L. PATRICK, Examiner. 

1. IN COMBINATION A FURNACE INTO WHICH FUEL AND AIR ARE INTRODUCED WITH THE FUEL BEING BURNED THEREWITHIN, MEANS FOR INTRODUCING INTO THE FURNANCE AN INERT GAS AND MEANS FOR SAMPLING THE FURNANCE ATMOSPHERE INCLUDING BURNER MEANS FOR BURNING THE FURNACE ATMOSPHERE AS RECEIVED FROM THE FURNACE, MEANS OPERATIVE TO REMOVE THE INERT GAS ADDED TO SAID ATMOSPHERE AND MEANS RECEIVING THE 